GB1455284A - Process for the preparation of disazo pigments - Google Patents

Abstract

1455284 Preparation of disazo pigments HOECHST AG 16 Nov 1973 [16 Nov 1972] 53309/73 Heading C4P Disazo pigments are prepared by diazotizing an aromatic amine which does not contain watersolubilizing groups with a nitrosyl compound in an aprotic water-miscible organic liquid and reacting the resulting diazonium salt solution with an N,N<SP>1</SP>-bis-(2-hydroxynaphth-3-oyl)-diamine coupling component in which each of the two substituted amino groups is attached directly to a carbon atom in an aromatic ring. Preferred nitrosyl compounds are nitrosylsulphuric acid and nitrosyl chloride and preferred organic liquids are dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethylsulphoxide, tetramethylenesulphone, tetramethylurea and hexamethylphosphoric triamide. The reactions are preferably carried out in an anhydrous medium but up to 50% of water may be present. The coupling components may be used in the form of their alkali metal salts. A base, e.g. pyridine, may be added to the reaction mixture during or after coupling; and coupling may be followed by a thermal aftertreatment, carried out preferably in the same solvent. Specified diazo components are 4 - chloro - 3 - amino - benzamide, anthranilic acid methyl ester 2-chloro-4-methyl-5-acetamido-aniline and 1-amino-2-methoxycarbonyl- 5-benzamide; and specified coupling components are N,N<SP>1</SP>-bis-(2<SP>1</SP>-hydroxy-naphth-3<SP>1</SP>- oyl)-1,4-diaminobenzene and coresponding compounds containing 2-methyl- and 2,5-dichlorosubstitution in the benzene ring, and N,N<SP>1</SP>-bis- (2 - hydroxy - naphth - 3 - oyl) - 4<SP>1</SP>,4<SP>11</SP> - diamino- 3<SP>1</SP>,3<SP>11</SP>-dimethoxy-diphenyl. The pigments may be used, for example, to colour lacquers and plastics materials, such as P.V.C. Specification 1,408,086 is referred to.